# Probing the coupling of axions to tops and gluons with LHC measurements

## TL;DR

This paper investigates axion-like particles with dominant gluon and top quark couplings, using LHC data and an effective field theory approach to set model-independent constraints on their properties.

## Contribution

It introduces a loop-aware EFT reinterpretation framework for LHC measurements to constrain ALPs with gluon and top couplings, accounting for radiative effects and EFT running.

## Key findings

- LHC data constrains ALP couplings to tops and gluons.
- EFT running and mixing significantly impact observable signals.
- The approach is extendable to other ALP interactions and signatures.

## Abstract

We study axion-like particles (ALPs) whose dominant interactions are with gluons and third-generation quarks, and whose couplings to light Standard Model (SM) particles arise at one loop. These loop-induced effects lead to ALP decays and production channels that can be probed at the LHC, even when tree-level couplings are absent. Using an effective field theory (EFT) description that includes momentum-dependent corrections from radiative effects, we reinterpret a wide range of LHC measurements via the CONTUR framework to derive model-independent constraints on the ALP parameter space. We show that LHC data place meaningful bounds in the plane of effective couplings $c^0_t/f_a$ and $c^0_{\tilde G}/f_a$, and that these limits are sensitive to the UV origin of the ALP-top and ALP-gluon couplings. We discuss representative scenarios where either $c^0_t$ or $c^0_{\tilde G}$ vanishes at the matching scale, and highlight the role of EFT running and mixing in generating observable signals. We also assess the domain of validity of the EFT approach by comparing the typical momentum transfer $\sqrt{\hat s}$ in sensitive regions to the underlying scale $f_a$. Our results demonstrate the power of loop-aware EFT reinterpretation of SM measurements in probing otherwise elusive ALP scenarios. The framework presented here can be readily extended to include couplings to other fermions and to accommodate ALP decay or long-lived signatures.